We had next to nothing in common until now, but I would like to welcome the Duchess of Cambridge to the mother-of-three club.

This exclusive gathering is not for the faint-hearted, especially if you, like me – and Kate – have three close together.

So what’s it really like having a trio of under-fives? I’ve been asked this by scared parents of-three-to-be and smug parents of one, most of whom still have time to brush their hair.

If you want to practice try taking three baby goats out for the day. Take them to a supermarket at peak shopping time. Try to steer them away from the sweetie aisle without being butted in the sternum and then attempt to strap them into the car for the journey home whilst fielding emergency calls on your mobile from friends.

These “friends” will constantly be on the line seeking help in the mistaken belief you are now free to assist with emergency child care are as you have clearly given up on adult life as we know it. You are now living permanently down with the kids, in a variety of stained t-shirts and slip on shoes.

Few mums have the luxury of being as glamorous as the Duchess of Cambridge. Photo : Chris Jackson/PA Wire (Image: PA)

Well, no, this is not strictly true. It is far worse than that.

First of all you have to deal with people’s responses. Some were impressed that as parents of two toddlers we were still having sex (well at least once anyhow). Others asked outright if our third was planned and a few childless “friends” expressed outrage that we were adding yet another human to an over populated planet.

If you thought people were nosy and judgemental with the first pregnancy that factor more than triples with the third. Still, it was the only time in my life I basked, however fleetingly, in the unexpected role of sex goddess in the eyes of my harassed friends of toddlers.

That came to an abrupt halt once I’d given birth. Here any similarities with Kate end. Frankly the medics were lucky I managed to get dressed at all afterwards. Sadly I did not think to pack heels in my hospital bag and with three under-fives it would be a few years before I tasted lipstick again.

But it was fabulous to be considered an experienced birther. The midwives let me get on with it and backed off when I barked that this time there was no way I was doing it on my back or with soothing music.

Back at the house life was about to change forever. One of the best things about having three so close together is that the world becomes an instant maelstrom so you have to be Zen about it. There’s no point swimming against the tide, you simply have to learn to ride the waves and go with the flow.

You can’t sweat the small stuff. If the curtains are stained and the four year-old hasn’t eaten a green vegetable for three weeks, so be it. As long as everyone is alive and scurvy is not imminent, you’re doing OK.

Getting ready for anything requires precision planning and takes three hours where 40 minutes once sufficed. On the upside you learn to grasp the good times as they come.

Forget what other people think about your domestic standards and if in doubt, cheat. When the health visitor came unannounced I stacked two days’ worth of washing up in the oven to hide the mess. It was a shame I later turned the oven on to heat up pizza without removing it.

Pizza, like wet wipes, will be your friend in the early days of shock and awe. Having three kids means never having to feel guilty about eating processed food.

It will be a necessity some days, especially in times of crisis, which may be often.

After supper bedtime beckons - for most of the rest of the night. Forget about sleep for a few years. You won’t get much so why worry? You’ll soon learn the art of dropping off whenever you can. In the cinema you’ll can snatch the odd 40 winks so encourage your children to enjoy screens.

Prince William arrives with Prince George and Princess Charlotte at the Lindo Wing after the Duchess of Cambridge gave birth to their son at St Mary's Hospital (Image: Chris Jackson/Getty Images)

Bedtime rituals with three very small people goes on for hours. The oldest and youngest will have different timings so you may be reading stories from 6pm to 8pm before starting all over again.

If any “super nanny” types mention that you ought to take a firm hand, send your three to stay with them for the weekend while you catch up on lost shut eye. By Sunday they will be begging for mercy and agreeing they know nothing.

Very quickly it will become clear that two arms and two legs are not enough. You cannot hold three hands in the same way as two. I once held on to a struggling toddler by the teeth - grabbing the edge of her coat in my mouth as she tried to run out of a playground. This, like many aspects of parenthood, is not recommended.

Holidays and days out can also be expensive as everything is based on the norm of two adults two children. But who wants the norm?

Far from being a crowd, three means safety, fun and joy in numbers. Games, parties, laughter, holidays - almost everything is better (if more expensive and chaotic) with more people.

Love expands like yeast and the kids will grow up loving the fact they outnumber the olds.

Now my three are 20, 18 and nearly 16, I can put to bed a few myths (if not a few toddlers). The middle one, far from being left out, has been buffered on both sides.

Growing up she was able to play up or down - as she puts it, she could watch Horrible Histories aged 12 without losing street cred because she said she was keeping her younger brother company. Equally she could go shopping in town with her teenage sister.

The oldest, far from being ignored, loved being the wise purveyor of life’s truths and advice from the tender age of four.

And the youngest? While we practised the art of parenting on his older sisters we were calmer and more chilled with him. His bed times have always been later, we fretted less about homework and nutrition.

The result. So far he is happy, has passed all exams and eats all his greens. Never nagged to eat broccoli, he loves it.